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Session for “Young” physicists

日程 : 2020年12月2日(水) 10:30 am - 12:00 pm 場所 : https://sites.google.com/view/cevis2020/registration (We will send the zoom link to the registered participants) 世話人 : 押川正毅 (ex.63275)
e-mail: oshikawa@issp.u-tokyo.ac.jp

Speaker 1: Byungmin Kang (KIAS)

Title: Superuniversality from disorder at two-dimensional topological phase transitions

Abstract: In this talk, I will investigate the effects of quenched randomness on topological quantum phase transitions in strongly-interacting two-dimensional systems. Using a combination of microscopically exact duality transformations and asymptotically exact real-space renormalization group techniques applied to these two-dimensional disordered gauge theories, I will argue that the resulting critical scaling behavior is `superuniversal’ across a wide range of such condensation transitions, and is controlled by the same infinite-randomness fixed point as that of the 2D random transverse-field Ising model. I will then validate this claim using large-scale quantum Monte Carlo simulations that allow us to extract zero-temperature critical exponents and correlation functions in (2+1)D disordered interacting systems. If time permits, I will discuss generalizations of these results to a large class of ground-state and excited-state topological transitions in systems with intrinsic topological order as well as those where topological order is either protected or enriched by global symmetries. When the underlying topological order and the symmetry group are Abelian, the results provide prototypes for topological phase transitions between distinct many-body localized phases.

Speaker 2: Kohei Kawabata (University of Tokyo)

Title: Non-Hermitian topology

Abstract: While topological phases were mainly investigated for Hermitian systems at equilibrium, non-equilibrium topological phases of non-Hermitian systems are attracting growing interest. One of the remarkable consequences of non-Hermiticity is new types of topological phases without Hermitian analogs. Here, we show that such intrinsic non-Hermitian topology leads to the non-Hermitian skin effect [1], which is anomalous localization due to non-Hermiticity. Furthermore, we develop a field-theoretic description of intrinsic non-Hermitian topological phases [2]. From the field-theoretic perspective, the non-Hermitian skin effect is shown to be a signature of an anomaly.

[1] N. Okuma, K. Kawabata, K. Shiozaki, and M. Sato, Phys. Rev. Lett. 124, 086801 (2020).
[2] K. Kawabata, K. Shiozaki, and S. Ryu, arXiv:2011.11449.

Chair: Gil Young Cho

This event is jointly organized by the Korea Institute for Advanced Study and the University of Tokyo. “Correlated Electrons Virtual International Seminars (CEVIS)” https://sites.google.com/view/cevis2020/home

 


(公開日: 2020年11月27日)